Bottom Line:
BRAF V600mut ctDNA decreased rapidly upon initiation of targeted therapy (p < 0.001) and became undetectable in 60 % of patients (n = 7/12) after 6 weeks of treatment.Quantitative analysis of BRAF V600mut ctDNA in plasma has unique features as a monitoring tool during treatment with BRAF/MEK inhibitors.Its potential as an early predictor of acquired resistance deserves further evaluation.

Methods: Allele-specific quantitative PCR analysis for BRAF V600 E/E2/D/K/R/M mutations was performed on DNA extracted from plasma of patients with known BRAF V600 mutant melanoma who were treated with dabrafenib and trametinib.

Results: 245 plasma samples from 36 patients were analyzed. In 16 patients the first plasma sample was obtained before the first dosing of dabrafenib/trametinib. At baseline, BRAF V600mut ctDNA was detected in 75 % of patients (n = 12/16). BRAF V600mut ctDNA decreased rapidly upon initiation of targeted therapy (p < 0.001) and became undetectable in 60 % of patients (n = 7/12) after 6 weeks of treatment. During treatment, disease progression (PD) was diagnosed in 27 of 36 patients. An increase of the BRAF V600mut ctDNA copy number and fraction, identified PD with a sensitivity of 70 % (n = 19/27) and a specificity of 100 %. An increase in the BRAF V600mut ctDNA fraction was detected prior to clinical PD in 44 % of cases (n = 12/27) and simultaneously with PD in 26 % of patients (n = 7/27).

Conclusions: Quantitative analysis of BRAF V600mut ctDNA in plasma has unique features as a monitoring tool during treatment with BRAF/MEK inhibitors. Its potential as an early predictor of acquired resistance deserves further evaluation.

Fig3: a Individual evolutions in the BRAF V600mut ctDNA fraction from initiation of treatment with dabrafenib (150 mg BID) and trametinib (2 mg QD), at baseline (BL) to the first visit (FV). b Individual evolutions in the BRAF V600mut ctDNA copy number from initiation of treatment with dabrafenib (150 mg BID) and trametinib (2 mg QD) at baseline (BL) to the first visit (FV)

Mentions:
During treatment, the BRAF V600mut ctDNA fraction and copy number decreased significantly compared to baseline in all 12 patients (p < 0.01, Fig. 3), and became undetectable (n = 7) or <1 % (n = 5) after a median of 13 days (range 6–40 days). At the time when no ctDNA could be measured any more, none of the patients had obtained a complete radiological remission (e.g. Fig. 4a, e). In 3 patients, BRAF V600mut ctDNA remained detectable from the initiation of targeted therapy until PD was diagnosed (e.g. Fig. 4b). Median PFS was not significantly longer for patients in whom BRAF V600mut ctDNA became undetectable 1 month after the initiation of targeted therapy, as compared to patients in whom ctDNA remained detectable during the first month of therapy (p = 0.56). Progression free survival was significantly shorter for patients in whom BRAF V600mut ctDNA remained detectable throughout the treatment with targeted therapy compared to patients in whom BRAF V600mut ctDNA became undetectable (p < 0.001) (Fig. 5).Fig. 3

Fig3: a Individual evolutions in the BRAF V600mut ctDNA fraction from initiation of treatment with dabrafenib (150 mg BID) and trametinib (2 mg QD), at baseline (BL) to the first visit (FV). b Individual evolutions in the BRAF V600mut ctDNA copy number from initiation of treatment with dabrafenib (150 mg BID) and trametinib (2 mg QD) at baseline (BL) to the first visit (FV)

Mentions:
During treatment, the BRAF V600mut ctDNA fraction and copy number decreased significantly compared to baseline in all 12 patients (p < 0.01, Fig. 3), and became undetectable (n = 7) or <1 % (n = 5) after a median of 13 days (range 6–40 days). At the time when no ctDNA could be measured any more, none of the patients had obtained a complete radiological remission (e.g. Fig. 4a, e). In 3 patients, BRAF V600mut ctDNA remained detectable from the initiation of targeted therapy until PD was diagnosed (e.g. Fig. 4b). Median PFS was not significantly longer for patients in whom BRAF V600mut ctDNA became undetectable 1 month after the initiation of targeted therapy, as compared to patients in whom ctDNA remained detectable during the first month of therapy (p = 0.56). Progression free survival was significantly shorter for patients in whom BRAF V600mut ctDNA remained detectable throughout the treatment with targeted therapy compared to patients in whom BRAF V600mut ctDNA became undetectable (p < 0.001) (Fig. 5).Fig. 3

Bottom Line:
BRAF V600mut ctDNA decreased rapidly upon initiation of targeted therapy (p < 0.001) and became undetectable in 60 % of patients (n = 7/12) after 6 weeks of treatment.Quantitative analysis of BRAF V600mut ctDNA in plasma has unique features as a monitoring tool during treatment with BRAF/MEK inhibitors.Its potential as an early predictor of acquired resistance deserves further evaluation.

Methods: Allele-specific quantitative PCR analysis for BRAF V600 E/E2/D/K/R/M mutations was performed on DNA extracted from plasma of patients with known BRAF V600 mutant melanoma who were treated with dabrafenib and trametinib.

Results: 245 plasma samples from 36 patients were analyzed. In 16 patients the first plasma sample was obtained before the first dosing of dabrafenib/trametinib. At baseline, BRAF V600mut ctDNA was detected in 75 % of patients (n = 12/16). BRAF V600mut ctDNA decreased rapidly upon initiation of targeted therapy (p < 0.001) and became undetectable in 60 % of patients (n = 7/12) after 6 weeks of treatment. During treatment, disease progression (PD) was diagnosed in 27 of 36 patients. An increase of the BRAF V600mut ctDNA copy number and fraction, identified PD with a sensitivity of 70 % (n = 19/27) and a specificity of 100 %. An increase in the BRAF V600mut ctDNA fraction was detected prior to clinical PD in 44 % of cases (n = 12/27) and simultaneously with PD in 26 % of patients (n = 7/27).

Conclusions: Quantitative analysis of BRAF V600mut ctDNA in plasma has unique features as a monitoring tool during treatment with BRAF/MEK inhibitors. Its potential as an early predictor of acquired resistance deserves further evaluation.